History of the Peloponnesian War

And following his advice they built the wall round the Peiraeus of the thickness that may still be observed; for two wagons carrying the stones could meet and pass each other. Inside, moreover, there was neither rubble nor mortar, but stones of large size hewn square were closely laid together, bound to one another on the outside with iron clamps and lead.

But the wall was completed to only about half of the height he originally intended, for what he wished was to be able to repel the assaults of the enemy by the very height and thickness of the wall, and he thought that a few men, and these the least effective, would suffice to guard it, while all the rest might man the ships.